Piping enhancement for backflow prevention in a multiple loop, metal cooled nuclear reactor system

ABSTRACT

A sodium-cooled nuclear reactor includes at least one electromagnetic pump assembly and a backflow reduction pipe. The backflow reduction pipe may include an inlet, an outlet, at least one tubular section having a first length and a first diameter, and at least one fluid diode section between the inlet and the outlet.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a Divisional application of U.S. application Ser.No. 14/960,511, filed Dec. 7, 2015, the entire contents of which isincorporated herein by reference.

BACKGROUND Field

The present disclosure relates to a backflow reduction pipe for anelectromagnetic pump.

Description of Related Art

Sodium-cooled nuclear reactors utilize electromagnetic pumps to flowsodium fluid from a heat exchanger to a bottom of a reactor core.Generally, four circuit pumps, each including two outlet pipes are used.If one pump is not operational, the other three pumps may force fluidflow back into the outlets of the non-operational pump.

SUMMARY

At least one example embodiment relates to a sodium-cooled nuclearreactor including a backflow reduction pipe.

In at least one example embodiment, a sodium-cooled nuclear reactorincludes at least one electromagnetic pump assembly and a backflowreduction pipe. The backflow reduction pipe may include an inlet, anoutlet, at least one tubular section having a first length and a firstdiameter, and at least one fluid diode section between the inlet and theoutlet. The at least one tubular section is between the inlet and theoutlet. The at least one fluid diode section may include a first sectionhaving a second diameter at a largest point of the first section, and asecond section having a third diameter at a largest point of the secondsection. The first section is closer to the inlet than the secondsection. The at least one fluid diode section is configured to restrictbackflow.

In at least one example embodiment, the second diameter is larger thaneach of the third diameter and the first diameter. The first section mayhave a first radius at a widest point thereof. The second section mayhave a second radius at a widest point thereof. The first radius isabout 1.9 to about 2.2 times the second radius of the second section.

In at least one example embodiment, the at least one fluid diode sectionhas a second length and the second section has a third length. Thesecond length is about 1.9 to about 2.2 times the third length of thesecond section.

In at least one example embodiment, the at least one fluid diode sectionhas a second length and the first section has a first radius at a widestpoint thereof. The second length of the at least one fluid diode sectionis about 2.1 to about 2.4 times the first radius of the first section.

In at least one example embodiment, the second section is generallycylindrical in cross-section. In at least one example embodiment, thefirst section is generally frustoconical in cross-section and the firstsection has a larger diameter towards an inlet end of the pipe and asmaller diameter towards an outlet end of the pipe.

In at least one example embodiment, the first section and the secondsection are generally frustoconical in cross-section.

In at least one example embodiment, the first section and the secondsection each have a larger diameter towards an inlet end of the pipe anda smaller diameter towards an outlet end of the pipe. The first sectionmay include a lobe. A portion of the lobe may overlap with a portion ofthe at least one tubular section.

In at least one example embodiment, the backflow reduction pipe includesa plurality of fluid diode sections along a length of the backflowreduction pipe. At least one of the plurality of fluid diode sectionsmay be centrally located along the length of the backflow reductionpipe. In at least one example embodiment, at least one of the pluralityof fluid diode sections is located adjacent the inlet of the backflowreduction pipe. In at least one example embodiment, at least one of theplurality of fluid diode sections is located adjacent the outlet of thebackflow reduction pipe.

In at least one example embodiment, the backflow reduction pipe includesa plurality of tubular sections. At least one of the plurality oftubular sections is between adjacent ones of the plurality of fluiddiode sections.

In at least one example embodiment, a flow from the outlet to the inletundergoes a pressure drop ranging from about 20 psi to about 25 psi. Inat least one example embodiment, a flow from the inlet to the outletundergoes a pressure drop ranging from about 5 psi to about 8 psi.

At least one example embodiment relates to a backflow reduction pipe.

In at least one example embodiment, a backflow reduction pipe for asodium-cooled nuclear reactor includes at least one tubular sectionhaving a length and a diameter and at least one fluid diode sectionconfigured to restrict backflow. The diameter of the at least onetubular section is generally uniform along the length of the at leastone tubular section. The fluid diode section may include at least oneportion having a larger diameter than the diameter of the at least onetubular section, the diameter of the at least one being about 1.9 toabout 2.2 times the diameter of the at least one tubular section.

At least one example embodiment relates to a method of reducing backflowin a sodium-cooled nuclear reactor.

In at least one example embodiment, a method of reducing backflow in asodium-cooled nuclear reactor includes installing a backflow reductionpipe in at least one electromagnetic pump assembly.

At least one example embodiment relates to a method of manufacturing abackflow reduction pipe.

In at least one example embodiment, a method of manufacturing a backflowreduction pipe includes 3D printing a pipe. The pipe may include atleast one tubular section having a diameter and at least one fluid diodesection configured to restrict backflow. The diameter of the at leastone tubular section is generally uniform along a length of the at leastone tubular section. The fluid diode section includes at least oneportion having a larger diameter than the diameter of the at least onetubular section. The diameter of the at least one portion is about 1.9to about 2.2 times the diameter of the at least one tubular section.

In at least one example embodiment, a method manufacturing a backflowreduction pipe includes machining a plurality of tubular sections, eachof the tubular sections having a generally uniform diameter along alength thereof, and machining a plurality of fluid diode sectionsconfigured to restrict backflow. Each of the fluid diode sectionsincludes at least one portion having a larger diameter than a diameterof each of the tubular sections. The diameter of the at least oneportion is about 1.9 to about 2.2 times the diameter of the tubularsections. The method also includes welding at least one of the pluralityof fluid diode sections between adjacent ones of the tubular sections.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of the non-limiting embodimentsherein may become more apparent upon review of the detailed descriptionin conjunction with the accompanying drawings. The accompanying drawingsare merely provided for illustrative purposes and should not beinterpreted to limit the scope of the claims. The accompanying drawingsare not to be considered as drawn to scale unless explicitly noted. Forpurposes of clarity, various dimensions of the drawings may have beenexaggerated.

FIG. 1 is a schematic illustration of a sodium-cooled nuclear reactorincluding a backflow reduction pipe according to at least one exampleembodiment.

FIG. 2 an enlarged view of a portion of a backflow reduction pipeaccording to at least one example embodiment.

FIG. 3 an enlarged view of a portion of a backflow reduction pipeaccording to at least one example embodiment.

FIG. 4 an enlarged view of a portion of a backflow reduction pipeaccording to at least one example embodiment.

FIG. 5 is an illustration of a backflow reduction pipe including spacedapart fluid diode sections according to at least one example embodiment.

FIG. 6 is an illustration of a backflow reduction pipe including atleast one fluid diode section near an inlet of the pipe according to atleast one example embodiment.

FIG. 7 is an illustration of a backflow reduction pipe including atleast one fluid diode section near an outlet of the pipe according to atleast one example embodiment.

FIG. 8 is an illustration of a backflow reduction pipe according to atleast one example embodiment.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Some detailed example embodiments are disclosed herein. However,specific structural and functional details disclosed herein are merelyrepresentative for purposes of describing example embodiments. Exampleembodiments may, however, be embodied in many alternate forms and shouldnot be construed as limited to only the example embodiments set forthherein.

Accordingly, while example embodiments are capable of variousmodifications and alternative forms, example embodiments thereof areshown by way of example in the drawings and will herein be described indetail. It should be understood, however, that there is no intent tolimit example embodiments to the particular forms disclosed, but to thecontrary, example embodiments are to cover all modifications,equivalents, and alternatives falling within the scope of exampleembodiments. Like numbers refer to like elements throughout thedescription of the figures.

It should be understood that when an element or layer is referred to asbeing “on,” “connected to,” “coupled to,” or “covering” another elementor layer, it may be directly on, connected to, coupled to, or coveringthe other element or layer or intervening elements or layers may bepresent. In contrast, when an element is referred to as being “directlyon,” “directly connected to,” or “directly coupled to” another elementor layer, there are no intervening elements or layers present. Likenumbers refer to like elements throughout the specification. As usedherein, the term “and/or” includes any and all combinations of one ormore of the associated listed items.

It should be understood that, although the terms first, second, third,etc. may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers, and/or sections should not be limited by these terms. Theseterms are only used to distinguish one element, component, region,layer, or section from another region, layer, or section. Thus, a firstelement, component, region, layer, or section discussed below could betermed a second element, component, region, layer, or section withoutdeparting from the teachings of example embodiments.

Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,”“upper,” and the like) may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It should be understood thatthe spatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” may encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

The terminology used herein is for the purpose of describing variousexample embodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an,” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“includes,” “including,” “comprises,” and/or “comprising,” when used inthis specification, specify the presence of stated features, integers,steps, operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Example embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of exampleembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, example embodiments should not be construed aslimited to the shapes of regions illustrated herein but are to includedeviations in shapes that result, for example, from manufacturing.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments belong. Itwill be further understood that terms, including those defined incommonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand will not be interpreted in an idealized or overly formal senseunless expressly so defined herein.

At least one example embodiment relates to a sodium-cooled nuclearreactor including a backflow reduction pipe.

FIG. 1 is a schematic illustration of a sodium-cooled nuclear reactorincluding a backflow reduction pipe according to at least one exampleembodiment.

In at least one example embodiment, as shown in FIG. 1, a sodium-coolednuclear reactor 10 includes a heat exchanger 20 and a reactor core 30.An electromagnetic pump 40 pumps sodium fluid from the heat exchanger 20to a bottom of the reactor core 30 so that the sodium fluid moves upwardthrough the reactor core 30. In at least one example embodiment, thesodium-cooled nuclear reactor 10 includes four electromagnetic pumps 40.Each pump includes a backflow reduction pipe 50 through which sodiumfluid flows from the heat exchanger 20 to the reactor core 30.

In at least one example embodiment, the backflow reduction pipe 50includes an inlet 52 in fluid communication with the heat exchanger 20and an outlet 54 in fluid communication with the reactor core 30. Thebackflow reduction pipe 50 includes at least one tubular section 56 andat least one fluid diode section 58. The fluid diode section 58 has ahigher resistance to flow in a first direction as compared to a seconddirection.

In at least one example embodiment, the at least one tubular section 56has a first length and a first diameter. The at least one tubularsection 56 is between the inlet 52 and the outlet 54.

In at least one example embodiment, the at least one fluid diode section58 includes a first section 62 and a second section 60. The firstsection 62 of each fluid diode section 58 is closer to the inlet 52 ofthe backflow reduction pipe 50 than the second section 60. In at leastone example embodiment, the first section 62 has a second diameter at alargest diameter of the first section 62. The second section 60 has athird diameter at a largest diameter of the second section 60. The atleast one fluid diode section 58 is configured to restrict backflow. Inat least one example embodiment, the second diameter is larger than eachof the third diameter and the first diameter.

In at least one example embodiment, the second section 60 is generallycylindrical in cross-section (not shown). In at least one exampleembodiment, the first section 62 is generally frustoconical incross-section and the first section 62 has a larger diameter towards theinlet 52 of the pipe 50 and a smaller diameter towards the outlet 54 ofthe pipe 50.

In at least one example embodiment, the first section 62 may include alobe 100 extending around a circumference of the first section 62. Aportion of the lobe 100 may overlap with a portion of the tubularsection 56 that is positioned between the inlet 52 and the first section62. An eddy current may form in the backflow direction (from outlet 54to inlet 52) at the lobe 100.

In at least one example embodiment, the first section 62 and the secondsection 60 are generally frustoconical in cross-section.

In at least one example embodiment, the first section 62 and the secondsection 60 each have a larger diameter towards the inlet 52 of the pipe50 and a smaller diameter towards the outlet 54 of the pipe 50.

In at least one example embodiment, the backflow reduction pipe includesa plurality of fluid diode sections 58 along a length of the backflowreduction pipe 50. At least one of the plurality of fluid diode sections58 may be centrally located along the length of the backflow reductionpipe 50.

In at least one example embodiment, a flow from the outlet 54 to theinlet 52 undergoes a pressure drop ranging from about 20 psi to about 25psi. In at least one example embodiment, a flow from the inlet 52 to theoutlet 54 undergoes a pressure drop ranging from about 5 psi to about 8psi.

In at least at one example embodiment, in a normal flow direction (frominlet 52 to outlet 54), the second section 60 increases forward velocityof the fluid to propel the fluid past the first section 62, which hasminimal effect on the forward flow of the fluid. In a backflow direction(from outlet 54 to inlet 52), a decrease in area as a result of thesecond section 60 increases pressure slightly, but eddies may be formeddue to fluid expansion in the first section 62, which may create a largepressure drop.

In at least one example embodiment, the second section 60 may restrictflow in the backflow direction without the use of moving parts andwithout additional electrical and/or control system interfaces. The flowrestriction forces flow from operable pumps to flow up through thereactor core 30 as opposed to back into inoperable pump. This increasesthe power output of the reactor during a pump shutdown. This alsoincreases operability as one of four pumps shutting down would otherwiserequire a reactor trip.

In at least one example embodiment, the fluid diode section 58 is formedof stainless steel or any other suitable material.

In at least one example embodiment, the backflow reduction pipe 50 maybe a single, uniform pipe. In other example embodiments, the fluid diodesection 58 is a separate piece that is welded or otherwise attachedbetween adjacent tubular sections 56. The first section 62 and thesecond section 60 of the fluid diode section 58 may be integrally formedor formed separately.

In at least one example embodiment, the backflow reduction pipe 50 isabout 10 feet to about 30 feet long. Each of the fluid diode sectionsmay be about 2 feet to about 6 feet long. The backflow reduction pipe 50may include one to ten fluid diode sections.

FIG. 2 an enlarged view of a portion of a backflow reduction pipeaccording to at least one example embodiment.

In at least one example embodiment, the first section 62 may have afirst radius (W1) at a largest diameter of the first section 62. Thesecond section 60 may have a second radius (W2) at a largest diameter ofthe second section 60. The first radius (W1) of the first section 62 isabout 1.9 to about 2.2 times the second radius (W2) of the secondsection 60.

FIG. 3 an enlarged view of a portion of a backflow reduction pipeaccording to at least one example embodiment.

In at least one example embodiment, the at least one fluid diode section58 has a second length (L1) and the second section 60 has a third length(L2). The second length (L1) is about 1.9 to about 2.2 times the thirdlength (L2) of the second section 60.

FIG. 4 an enlarged view of a portion of a backflow reduction pipeaccording to at least one example embodiment.

In at least one example embodiment, the at least one fluid diode section58 has the second length (L1) and the first section 62 has the firstradius (W1) at a widest point thereof. The second length (L1) of the atleast one fluid diode section 58 is about 2.1 to about 2.4 times thefirst radius (W1) of the first section 62.

FIG. 5 is an illustration of a backflow reduction pipe including spacedapart fluid diode sections according to at least one example embodiment.

In at least one example embodiment, the backflow reduction pipe 50includes a plurality of tubular sections 56. At least one of theplurality of tubular sections 56 is between adjacent ones of theplurality of fluid diode sections 58. The length of each of the tubularsection 56 may vary, and a pattern of tubular sections 56 and fluiddiode sections 58 may be formed along the length of the backflowreduction pipe 50.

FIG. 6 is an illustration of a backflow reduction pipe including atleast one fluid diode section near an inlet of the pipe according to atleast one example embodiment.

In at least one example embodiment, at least one fluid diode section 58is located adjacent the inlet 52 of the backflow reduction pipe 50. Inat least one example embodiment, at least one fluid diode section 58 islocated closer to the inlet 52 of the backflow reduction pipe 50 thanthe outlet 54 of the backflow reduction pipe 50.

FIG. 7 is an illustration of a backflow reduction pipe including atleast one fluid diode section near an outlet of the pipe according to atleast one example embodiment.

In at least one example embodiment, at least one fluid diode section 58is located adjacent to the outlet 54 of the backflow reduction pipe 50.In at least one example embodiment, at least one fluid diode section 58is located closer to the outlet 54 of the backflow reduction pipe 50than the inlet 52.

FIG. 8 is an illustration of a backflow reduction pipe according to atleast one example embodiment.

In at least one example embodiment, as shown in FIG. 8, the backflowreduction pipe 50 may have a substantially uniform outer diameter. Aninner diameter of the backflow reduction pipe 50 may vary along a lengththereof to form the tubular section 56 and the fluid diode section 58including the first section 62 and the second section 60 within thebackflow reduction pipe 50.

Sodium-cooled nuclear reactors utilize electromagnetic pumps to flowsodium fluid from a heat exchanger to a bottom of a reactor core.Generally, four circuit pumps, each including two outlet pipes are used.If one pump is not operational, the other three pumps may force fluidflow back into the outlets of the non-operational pump.

The addition of a fluid diode section 58 to the backflow reduction pipeaids in forming a pressure gradient in the backflow direction withoutdisrupting flow in the normal direction. Thus, the backflow reductionpipe provides flow resistance in the backflow direction withoutdisrupting the natural circulation pathway, and allows for operationapproaching 75% of rated power with three pump operation. The backflowreduction pipe improves the operability and reliability of sodium pumpedsystems.

Using computational fluid dynamic (CFD) analysis, a generally straightpipe (not shown) may have a pressure drop of about 0.2 psi, and the flowresistance is the same in either direction. In contrast, also using theCFD analysis, the backflow resistance pipe 50 having a same length asthe straight pipe is expected to increase pressure drop from about 0.2psi to about 6 psi. When flow is reversed (from outlet 54 to inlet 52),the pressure is expected to go up about four times or to about 24 psi.Thus, compared to a straight pipe, a substantial increase in flowresistance due to backflow may be demonstrated. In addition, forwardvelocity through the second section 60 may be accelerated to allow abypass of the geometric first section 62. The backflow direction mayshow a substantial eddy formation adjacent the lobes 100 of the firstsection 62.

The increase in core flow, which is directly correlated with reactorpower, may be calculated compared to a pipe under a single pump tripscenario using the CFD analysis data. Assuming that a pump pipingnominally causes a 5 psi pressure drop in addition to the fluid diodesection 58 pressure drop, the core flow increases from about 34% togreater than 52% out of a possible 75%. The 18% increase in core flowfor a single reactor corresponds to about a 54 MW increase.

In at least one example embodiment, the use of the backflow reductionpipe 50 prevents the need to trip a reactor running on multipleindependent electromagnetic pumps when one of the pumps fails. The useof the backflow reduction pipe 50 provides a way to keep the heatexchange flow in the correct direction while producing steam at areduced rate. In addition, the backflow reduction pipe 50 may be modularso that the pipe 50 can be tailored for specific conditions. Thecombination of the first section 62 and the second section 60 increasesefficiency of pressure ratio. The backflow reduction pipe 50 also allowsbetter coolant mixing in either direction and increases the life timecapacity factor through operation during single pump failure.

At least one example embodiment relates to a method of reducing backflowin a sodium-cooled nuclear reactor.

In at least one example embodiment, a method of reducing backflow in asodium-cooled nuclear reactor includes installing a backflow reductionpipe in at least one electromagnetic pump assembly.

At least one example embodiment relates to a method of manufacturing abackflow reduction pipe.

In at least one example embodiment, a method of manufacturing a backflowreduction pipe 50 includes 3D printing the backflow reduction pipe 50.The pipe 50 may include at least one tubular section 56 having adiameter and at least one fluid diode section 58 configured to restrictbackflow. One or more of the at least one tubular section 56 and the atleast one fluid diode section 58 may be 3D printed. In at least oneexample embodiment, the at least one tubular section 56 and the at leastone fluid diode section 58 are integrally formed via 3D printing. Thediameter of the at least one tubular section 56 is generally uniformalong a length of the at least one tubular section 56. The fluid diodesection 58 includes at least one portion having a larger diameter thanthe diameter of the at least one tubular section 56. The diameter of theat least one portion is about 1.9 to about 2.2 times the diameter of theat least one tubular section.

In at least one example embodiment, a method manufacturing a backflowreduction pipe includes machining a plurality of tubular sections 56.Each of the tubular sections 56 may have a generally uniform diameteralong a length thereof. The method may also include machining aplurality of fluid diode sections 58 that are configured to restrictbackflow. Each of the fluid diode sections 58 may include at least oneportion having a larger diameter than a diameter of each of the tubularsections 56. The diameter of the at least one portion is about 1.9 toabout 2.2 times the diameter of the tubular sections 56. The method mayalso include welding at least one of the plurality of fluid diodesections 58 between adjacent ones of the tubular sections 56.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

We claim:
 1. A method of manufacturing a backflow reduction pipecomprising: 3D printing a pipe, the pipe comprising: at least onetubular section having a diameter, the diameter being generally uniformalong a length of the at least one tubular section; and at least onefluid diode section configured to restrict backflow, the fluid diodesection including, at least one portion having a larger diameter thanthe diameter of the at least one tubular section, the diameter of the atleast one portion being about 1.9 to about 2.2 times the diameter of theat least one tubular section.
 2. A method manufacturing a backflowreduction pipe comprising: machining a plurality of tubular sections,each of the tubular sections having a generally uniform diameter along alength thereof; machining a plurality of fluid diode sections configuredto restrict backflow, each of the fluid diode sections including, atleast one portion having a larger diameter than a diameter of each ofthe tubular sections, the diameter of the at least one portion beingabout 1.9 to about 2.2 times the diameter of the tubular sections; andwelding at least one of the plurality of fluid diode sections betweenadjacent ones of the tubular sections.